Fluid distribution emitters are used in many applications where fluid needs to be distributed over a large area and in a slow and controlled rate. One application is in mining where chemistry is distributed over large collections of material such as copper ore or gold ore to leach materials out of the ore. Such systems largely solved the problem of chemicals being sprayed or sprinkled onto the leaching field, such as the fluid freezing as it is blown into the air at high elevations, and dispersion of hazardous chemicals into adjacent areas. Emitters are also used in drip irrigation systems where the flow rate needs to be carefully controlled. Thus, the present invention may be usable in a wide variety of mining, agriculture and landscape settings. In each setting, it is desirable to control the amount of fluid that flows through such a system over a given period of time. Flow rates are typically measured in liquid volume per unit of time, such as gallons per hour (gph).
Historically, such flow-rate devices can be susceptible to plugging due to many factors, such as the presence of particulates like leaching chemicals precipitating out of fluid being distributed, scale build up due to water hardness, introduction of carbon used in treatment processes into the drip lines, and sediment settling into the screens of emitters that are downwardly facing. Such particulates may also result from sediment in an irrigation water source or contamination of the irrigation water source.
Typically, emitters designed to achieve lower flow rates are more susceptible to such plugging. In both mining and agricultural settings, the lower the pressure, the lower the flow rate will be, and the more susceptible the system will be to plugging. Plugging can also occur as a result of pressure fluctuations and changes in elevation. Plugged emitters are in many ways more problematic than no emitters at all because the operator will assume that fluid is being evenly distributed across the leach field or to the plants being irrigated, when in fact none of that is happening at all.
While employing filters to remove contaminants in leaching and irrigation systems may reduce the frequency of plugging in flow-rate control devices, filters are typically expensive, and their use may be cost prohibitive in certain applications. Moreover, filtration systems often cannot be included at enough spots along the lines to prevent blockages. Therefore, alternatives to conventional flow rate control devices are desirable.
One effective solution to the plugging problem has been the development of an inline emitter, that is, one that is positioned within and coaxial with the extension of the tubing. One such emitter is disclosed in U.S. Pat. No. 6,817,548 and has been marketed by R.M. Wade & Co. as the Max Emitter®. This emitter is shown in FIG. 1 and has been highly successful in overcoming the plugging problem with conventional emitters. However, emitter flow rates have been reduced lower and lower and the spacing between the emitters is getting increasingly small in order to more evenly distribute fluid in both irrigation and mining applications. For example, while in the past emitters might have been on a 24 inch spacing for irrigation applications and 32 inch spacing for mining, such spacing might now be on 12 inch and 15 inch spacing, respectively. This has dramatically increased the cost of emitting operations and resulted in the use of smaller and less expensive emitters.
One such smaller emitter is the so-called pill or flat emitter, which is positioned on one side of a tubing line. One such emitter is shown in FIGS. 1B and 1C. This emitter is very small in size and can be used in lightweight tubing, and is therefore less expensive than other solutions proposed for the plugging problem. However, the flat emitter is, like some earlier units, susceptible to plugging because, like older-style emitters, it is positioned on one side of the tubing and, if positioned on the downward side of the emitter line as shown in FIG. 1B, it can quickly become plugged and nonfunctional because sediment will settle into its grids, which is the small, lower stepped down area to the left side of the emitter in FIG. 1B. Also, given that pill emitters typically have only a single hole through which fluid is expected to flow to the leach field or the plantings, particulate in the fluid can easily plug that single source of fluid distribution.